The present invention is directed towards document scanning apparatus. Such apparatus are configured to optically scan an essentially flat document using an optical scanning device. The optical scanning device generates a stream of signals as the document is scanned. The signals, typically in an analog form, can then be converted into a digital form using known analog-to-digital conversion techniques. The resulting digital signals collectively comprise a representation of the scanned portion of the original document, and can be stored as a digital file or processed to generate a copy or a displayed image of the original document. Further, the digital document file can be further processed to modify the digital representation of the original document. For example, the document file can be modified to resize or re-orient the document with respect to the format in which it originally appeared. Most document scanning apparatus are in the form of a flat-bed scanner. That is, the scanning apparatus includes a transparent (usually glass) platen on which a document can be placed. A cover, which is hingedly attached to the main body of the scanning apparatus, can be closed over a document placed on the platen in order to reduce ambient light intrusion which can adversely affect the quality of the scanned image. Once a document is placed on the platen, the optical scanning device is then moved past the platen in order to scan the document. In another configuration, a document scanning apparatus can include a document sheet feeder which is configured to feed one or more sheets of a document into position for optical scanning. Two common configurations are used. In the first configuration, the optical scanning device remains static while the document is moved past the scanning device. In the other configuration, a transfer device, such as a belt, is used to move the document onto the platen. The scanning device is then moved past the document to thereby scan the document, and the document is then subsequently removed from the platen by the transfer device. A hybrid configuration allows the scanning device to remain static when a sheet feeder is used to transfer the document to the scanning device, but when a document is manually placed on the platen, the scanning devices moves past the document. Although most document scanning apparatus have a platen over which a document can be placed for scanning, in a less common configuration no platen is provided, and the document is moved past a static optical scanning device by a sheet feeder. This latter configuration is commonly found in facsimile machines, which can also function as a scanning apparatus.
The advantage of the flat-bed scanning arrangement is that documents (as well as other objects) of various sizes and shapes, which cannot be easily accommodated by a sheet feeder, can be scanned. However, when a document to be scanned exceeds the size of the platen, certain problems result. Turning to FIG. 1, a prior art scanning apparatus 10 is depicted in a plan view. The scanning apparatus 10 is also depicted in a sectional side elevation view in FIG. 2. With reference to FIGS. 1 and 2, the prior art scanning apparatus includes a scanner base 30 and a scanner cover 12. The scanner base supports a platen 25 and an optical scanning device 28. The cover 12 is attached to the base 30 by hinges 14, allowing the cover to be moved in direction “Q” (FIG. 2) so that a document can be placed on the platen 25. In the embodiment shown, the cover 12 includes a sheet feeder. A sheet of media (such as paper) can be placed in the input tray 16 (FIG. 1). A pick-roller 24 (FIG. 2) can then engage the sheet of media and move it in feed direction “F” (FIG. 1) past the optical scanning device 28 (FIG. 2) using the feed rollers 26. The scanned sheet is then discharged at output area 27. Alternately, a sheet of media can be placed directly on the platen 25 and the optical scanning device 28 can be moved past the sheet using a scanner drive mechanism (not shown). As can be seen in FIG. 1, the sheet feeding section of the cover 12 can induced a fixed upper-edge document guide 18 and a moveable lower edge document guide 22 which is configured to move on track 22 in directions “A”. A document sheet having a maximum width “W” can thus be accommodated by the sheet feeder. Typically, the width “W” is the maximum width of the scannable area of the platen 25 (i.e., the area which can be scanned by the scanning device 28). When a document is placed directly on the platen, then the scanning device 28 is limited to scanning an area of length “L” (FIG. 2).
Turning to FIG. 3, the prior art scanning apparatus 10 of FIGS. 1 and 2 is depicted in a plan view, but with the scanner cover 12 in an open position. Also depicted is an outline of an oversized document “D” which is positioned with the upper left corner “UL” of the document oriented in the upper left corner of the platen 25. The document “D”, being of width “WD” and length “LD”, is considered “oversized” since at least one of (and in this case, both) the length (LD) and width (WD) of the document “D” exceeds the respective length “L” and width “W” of the scannable area of the platen 25. As is evident, the optical scanning device 28 will not be able to scan the entire document “D” in a single scan.
When a sheet feeding device is used, such as is depicted in FIGS. 1 and 2, then a document with a document length “LD” greater than the scannable area length “L” can be scanned in a single pass, since the document can be moved past the optical scanning device 28 while the device 28 remains static. However, if the width “WD” of the document “D” exceeds the width “W” of the scannable area of the platen 25, then the sheet feeding device is of no help. Further, if the scanning apparatus 10 is not provided with a sheet feeder (typically at extra cost), then the optical scanner 28 will not be able to scan a document in a single pass where the length “LD” of the document “D” is greater than the length “L” of the scannable area. In the situation depicted in FIG. 3, a user is presented with essentially only one solution if the user desires to scan the entire area of the document “D”. That is, the user must manually move the document “D” over the platen 25 a number of times in order to scan the entire area of the document. In the example depicted, the user will need to make a first scan in the position shown. The user will then need to shift the document to the left to encompass the upper right corner “UR” of the document, then shift the document up to encompass the lower right corner “LR” of the document, and then to the right to encompass the lower left corner “LL” (or some combination of these various movements).
The above-described movements of the document “D” of FIG. 3 by a user in order to completely scan the area of the document present a number of problems. First of all, the cover 12 presents an impediment to the document and to movement of the document. If the document “D” is of a relatively stiff media (such as cardstock), then the cover 12 can require bending of the document in order to place the document on the platen 25. This can result in damage to the document. While the document can conceivably be rotated to various positions to avoid interference by the scanner cover 12, and thus avoid bending the document, this is only feasible when the document length “LD” and the document width “WD” are each shorter than the platen length “L” and width “W”. Removing the cover from the scanner base may be of some help in allowing the document to be moved around on the platen. However, this can require a significant amount of work and may result in damage to the scanning apparatus since the covers are typically not intended to be removed by a user. In addition, removing the cover will allow more light to intrude into the scanner during the scanning process, resulting in a low quality final image.
Further, while it is possible to scan the entire document by manually repositioning the document and making a plurality of scans, the result is a plurality of scanned images, rather than a single scanned image. In most instances, the user will desire a single scanned image. Accordingly, in order to acquire a single scanned image of an oversized document, a user will need to assemble a plurality of single scanned images to obtain a single scanned image. This can be done using known image processing software, but the process is difficult to do at best since matching the edges of the various scanned images requires significant image manipulation. Also, in many cases the user is merely guessing where to place the oversized document on the platen to scan the next segment, and the result can be overlapping portions between scanned images, or missing portions which require the user to re-scan the segment.
What is needed then is a document scanning apparatus which achieves the benefits to be derived from similar prior art apparatus, but which avoids the shortcomings and detriments individually associated therewith.